Electronic driving stability programs of commercial vehicles require the axle loads, particularly of the rear axle, as input variables. Up to now, the axle loads have been measured via axle load sensors, for example, by an air spring bellows pressure sensor for measuring the spring bellows pressure in an air suspension or by a travel sensor for measuring the compression travel in a steel spring suspension.
Alternatively, the axle loads may also be determined or estimated indirectly from other variables. In some electronic brake systems of commercial vehicles, the braking force distribution to the axles is based on a differential slip analysis. A differential slip controller for controlling the differential slip between the axles during braking is used for harmonizing the braking of the individual axles. From the differential slip and the braking reinforcement, one may then calculate the axle loads on the supposition that the braking characteristics values, such as frictional values of the brake linings and the brake disks are known. This type of calculation of the axle loads has, however, some disadvantages:                the axle loads are able to be calculated only after a sufficient number of brakings that are able to be evaluated,        values that are inaccurate and values that are only estimated enter into the calculated axle loads via the braking characteristics value, which, however, exert a considerable influence on the calculated result,        the braking force distribution always includes the dynamic axle load distribution which, however, is a function of the extent of the braking in a nonlinear manner. This further increases the inaccuracy of the axle loads calculated therefrom.        